China Geology最新文献

The Daheishan supergiant porphyry molybdenum deposit (also referred to as the Daheishan deposit) is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons, an average molybdenum ore grade of 0.081%, and molybdenum resources of 1.09 million tons. The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons, with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons. Specifically, it appears as an ore pipe with a large upper part and a small lower part, measuring about 1700 m in length and width, extending for about 500 m vertically, and covering an area of 2.3 km². Mineralogically, the main ore body consists of molybdenite, chalcopyrite, and sphalerite horizontally from its center outward and exhibits molybdenite, azurite, and pyrite vertically from top to bottom. The primary ore minerals include pyrite and molybdenite, and the secondary ore minerals include sphalerite, chalcopyrite, tetrahedrite, and scheelite, with average grades of molybdenum, copper, sulfur, gallium, and rhenium being 0.081%, 0.033%, 1.67%, 0.001%, and 0.0012%, respectively. The ore-forming fluids of the Daheishan deposit originated as the CO₂-H₂O-NaCl multiphase magmatic fluid system, rich in CO₂ and bearing minor amounts of CH₄, N₂, and H₂S, and later mixed with meteoric precipitation. In various mineralization stages, the ore-forming fluids had homogenization temperatures of > 420°C–400°C, 360°C–350°C, 340°C–230°C, 220°C–210°C, and 180°C–160°C and salinities of > 41.05%–9.8% NaCleqv, 38.16%–4.48% NaCleqv, 35.78%–4.49% NaCleqv, 7.43% NaCleqv, and 7.8%–9.5% NaCleqv, respectively. The mineralization of the Daheishan deposit occurred at 186–167 Ma. The granites closely related to the mineralization include granodiorites (granodiorite porphyries) and monzogranites (monzogranite porphyries), which were mineralized after magmatic evolution (189–167 Ma). Moreover, these mineralization-related granites exhibit low initial strontium content and high initial neodymium content, indicating that these granites underwent crust-mantle mixing. The Daheishan deposit formed during the Early-Middle Jurassic, during which basaltic magma underplating induced the lower-crust melting, leading to the formation of magma chambers. After the fractional crystallization of magmas, ore-bearing fluids formed. As the temperature and pressure decreased, the ore-bearing fluids boiled drops while ascending, leading to massive unloading of metal elements. Consequently, brecciated and veinlet-disseminated ore bodies formed.

©2023 China Geology Editorial Office.

To reveal the microbial community composition of regional shallow porous brackish groundwater and its response characteristics to groundwater environment, the first and second aquifers in Taocheng District, Hengshui City were selected, and 10 groundwater source samples were collected for hydrochemical analysis and microbial 16S RNA gene V4–V5 regional sequencing. The results showed that the shallow brackish groundwater in the study area is weakly alkaline and has high ion content. The hydrochemical types are SO₄·Cl-Na·Mg type and HCO₃·Cl-Na·Mg type as a whole. The spatial zonation of the abundance and diversity of groundwater microorganisms is obvious. The number of endemic bacteria in groundwater from upstream, midstream to downstream is 11, 135 and 22 respectively, with a total of 22 bacteria. Proteobacteria is the most dominant in groundwater level (38.82%–86.88%), and there are obvious differences in different sections. At the genus level, the main dominant species in each group and sample are Pseudomonas and Hydrogenophaga. In terms of composition difference, Pseudohongiella, Pseudorhodobacter and Limnohabitans are the representatives of UR, MR and LR. On the whole, the composition of flora in groundwater in the study area is sensitive and closely related to hydrochemical processes. Species abundance is affected by alkaline and high salinity environmental indicators, while species diversity is related to depth and dissolved oxygen in weak reduction environment.

©2023 China Geology Editorial Office.

The Luan River is the most important water system in north-eastern Hebei Province, China and is located in the transitional zone of the Eastern Yan Mountains, North China Plain and Songliao Plain. The well-developed river terraces of its tributary, the Yixun River, provide excellent information for studying neotectonics and climate change. There are seven terraces in the lower reaches of the Yixun River, numbered T7–T1. The optically stimulated luminescence dating results of 23 samples show that terraces T7–T2 formed at 111.36±5.83 ka, 78.20±4.45 ka, 65.29±4.15 ka, 56.44±3.07 ka, 40.08±2.66 ka, and 13.14±0.76 ka, respectively. A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e, MIS 3, and MIS 1. Since the Late Pleistocene, the incision rate of the Yixun River has ranged from 0.371–1.740 mm/a. During the formation of T7–T6, T5–T4, T4–T3, and T3–T2, the incision rate was low. However, in the two stages during which T6–T5 and T2–T1 formed (13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka), these rates reached 1.554 mm/a and 1.592–1.740 mm/a, respectively. At approximately 30 ka, the activity of the Langying Fault increased, leading to footwall uplift. The river gathered in the north of Langying to form the ancient Erdaowan Lake, which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits. In the Early Holocene, headward erosion in the lower reaches of the Yixun River was enhanced, which resulted in the disappearance of the lake, and incised meandering formed due to increased neotectonism. Based on the analyses of river incision and the formation of ancient lakes and incised meandering, it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.

©2023 China Geology Editorial Office.

To illuminate the spatio-temporal variation characteristics and geochemical driving mechanism of soil pH in the Nenjiang River Basin, the National Multi-objective Regional Geochemical Survey data of topsoil, the Second National Soil Survey data and Normalized Difference Vegetation Index (NDVI) were analyzed. The areas of neutral and alkaline soil decreased by 21100 km² and 30500 km², respectively, while that of strongly alkaline, extremely alkaline, and strongly acidic soil increased by 19600 km², 18200 km², and 15500 km², respectively, during the past 30 years. NDVI decreased with the increase of soil pH when soil pH > 8.0, and it was reversed when soil pH < 5.0. There were significant differences in soil pH with various surface cover types, which showed an ascending order: Arbor < reed < maize < rice < high and medium-covered meadow < low-covered meadow < Puccinellia. The weathering products of minerals rich in K₂O, Na₂O, CaO, and MgO entered into the low plain and were enriched in different parts by water transportation and lake deposition, while Fe and Al remained in the low hilly areas, which was the geochemical driving mechanism. The results of this study will provide scientific basis for making scientific and rational decisions on soil acidification and salinization.

©2023 China Geology Editorial Office.

Groundwater with high arsenic (As) content seriously threatens human life and health. Drinking high-As groundwater for a long time will lead to various pathological changes such as skin cancer, liver cancer, and kidney cancer. High-As groundwater has become one of the most serious environmental geological problems in China and even internationally. This paper aims to systematically summarize the sources, migration, distribution, toxicological effects, and treatment techniques of As in natural groundwater in China based on a large number of literature surveys. High-As groundwater in China is mainly distributed in the inland basins in arid and semi-arid environments and the alluvial and lacustrine aquifers in river deltas in humid environments, which are in neutral to weakly alkaline and strongly reducing environments. The content of As in groundwater varies widely, and As(III) is the main form. The main mechanism of the formation of high-As groundwater in China is the reduced dissolution of Fe and Mn oxides under the action of organic matter and primary microorganisms, alkaline environment, intense evaporation and concentration, long-term water-rock interaction, and slow groundwater velocity, which promote the continuous migration and enrichment of As in groundwater. There are obvious differences in the toxicity of different forms of As. The toxic of As(III) is far more than As(V), which is considered to be more toxic than methyl arsenate (MMA) and dimethyl arsenate (DMA). Inorganic As entering the body is metabolized through a combination of methylation (detoxification) and reduction (activation) and catalyzed by a series of methyltransferases and reductases. At present, remediation methods for high-As groundwater mainly include ion exchange technology, membrane filtration technology, biological treatment technology, nanocomposite adsorption technology, electrochemical technology, and so on. All the above remediation methods still have certain limitations, and it is urgent to develop treatment materials and technical means with stronger As removal performance and sustainability. With the joint efforts of scientists and governments of various countries in the future, this worldwide problem of drinking-water As poisoning will be solved as soon as possible. This paper systematically summarizes and discusses the hot research results of natural high-As groundwater, which could provide a reference for the related research of high-As groundwater in China and even the world.

©2023 China Geology Editorial Office.

The Pearl River Mouth Basin (PRMB) is one of the most petroliferous basins on the northern margin of the South China Sea. Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history. Our investigations in this study are based on apatite fission-track (AFT) thermochronology analysis of 12 cutting samples from 4 boreholes. Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution. Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene. The cooling events occurred approximately in the Late Eocene, early Oligocene, and the Late Miocene, possibly attributed to the Zhuqiong II Event, Nanhai Event, and Dongsha Event, respectively. The erosion amount during the first cooling stage is roughly estimated to be about 455–712 m, with an erosion rate of 0.08–0.12 mm/a. The second erosion-driven cooling is stronger than the first one, with an erosion amount of about 747–814 m and an erosion rate between about 0.13–0.21 mm/a. The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m, which is speculative due to the possible influence of the magmatic activity.

©2023 China Geology Editorial Office.